The National Air an Space Museum (NASM) of the Smithsonian Institution is a museum in Washington, D.C., United States, and is the most popular of the Smithsonian museums. It maintains the largest collection of aircraft and spacecraft in the world. It is also a vital center for research into the history, science, and technology of aviation and spaceflight, as well as planetary science and terrestrial geology and geophysics. Almost all space and aircraft on display are originals or backup crafts to the originals.